the butterfly effect
Discussion
I was having a lovely day at gurston hill climb with my griff. I did a personal best in practice to take the lead in the event. BUT as I got on the final straight my battery warning light came on because the alternator had failed - ok no worries I thought - just keep my foot hard down. This is where the butterfly effect comes in - the alternator drives the electric power steering pump so when I got to the last slight kink and over the finish I tried to turn and the steering didn't react quickly enough so off into the field. I only just managed to keep it out of the wall. So now I need a new alternator, 2 new front tyres to replace the now flat spotted ones and refit the exhaust which was knocked about - oh and some new underpants. who says motorsport isn't fun.
https://youtu.be/rE11rQtIn20
https://youtu.be/rE11rQtIn20
phazed said:
Are you sure it wasn't your 100 amp fuse?
I took a dedicated feed from the battery through another fuse link to my PS pump.
that was suggested on the day. but I don't think my car has one. we jacked it up and had a good look form beneath and there are no cables etc on the chassis only feeds to the starter the usual earths and small wires to the oil sender plus wires ofr the fans, lights etc at the front.. where is it normally located?I took a dedicated feed from the battery through another fuse link to my PS pump.
The AA chap who recovered me tested the alternator and said it was not putting out any current.
I think I will do the same as you - I assume that you have the switch box so the pump only runs on demand?
t' moment.I see the finish speed trap shows 112mph, even allowing for the fact it seemed a little optimistic you were plainly “pressing on”
Last time I spun there I also acquired a “side exit” exhaust system.
Since then I have always refrained from lifting until well into the breaking area, I was convinced my spin was caused by engine braking while the car was still unsettled by the finish kink.
Last time I spun there I also acquired a “side exit” exhaust system.
Since then I have always refrained from lifting until well into the breaking area, I was convinced my spin was caused by engine braking while the car was still unsettled by the finish kink.
jesfirth said:
phazed said:
Our cars are over alternatored. You will get away with a lower output.
thanks much appreciated -ordering a 70amp one...Be aware a 70amp alternator may only give you 30amps or so at idle, with this in mind it may be worth considering your true demand, especially at idle with the rad fans and your electric power steering pump running
I plotted my current demand on petrol & LPG which looks like this:
Keep in mind there's no electric power steering pump or headlights included in my above table, my figures suggested at idle without headlights or driving lights on my old 100amp alternator had things covered, and even with all the lights on and running LPG it was still just coping, but as soon as you throw the rad fans into the mix the story became very different.
If my fan figures look high its because I'm using the current spike numbers, it's important to accept there will always be a significant current spike way above normal fan operation draw at the moment they chime in, there's a very good reason why each rad fan was given it's own 25a fuse and 30a relay
. With this in mind now have a look at all the fuse values on a Chimaera/Griffith!
Your electric power steering pump which as a non-standard part would clearly be an addition to the above values, as I say I dont have one myself (just the standard engine driven pump) but even without the extra demand an electric pump would make on the system my figures still told me that upgrading the standard 100amp alternator to a 120a unit might be a smart move, the 10a increase at idle it offers would definitely be be advantageous under certain conditions.
A key fact often overlooked is the behavior of current sensitive components like the ECU, injectors and idle air control valve (stepper motor) which will all be negatively impacted if you don't design in sufficient alternator output head space, clearly the battery acts as a giant capacitor in the system which helps a lot to cover spikes and any immediate current deficit.... but there is always going to be a limit to what the battery can achieve before engine behavior and air fuel ratios start to go awry at idle and even in the shunting zone!
My last point is also why it's so important to have a good super healthy battery of a suitable size and capacity, it's also why it's critical all earths are clean and functioning without excessive resistance, finally its also why it's a very good idea to replace the feeble string thin +12v battery cable TVR used with something new and of a more suitable (read thicker) gauge.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
All this really didn't matter years ago when we ran fairly low powered ignition systems and carburetors, but as soon as we moved into the world of engine management the stability of the vehicles whole electrical system started to become very important indeed, and I'm damn sure TVR didn't give this important point nearly enough consideration when designing and executing the wiring of their cars.
I'd argue a really good battery, some additional earths, and the above cable upgrade I did years ago would go a long way to help every TVR owner enjoy a far more stable idle and urban driving experience.... especially at the moment the rad fans chime in and current spike. Lets face it the quality of the TVR wiring was (at best) only adequate when brand new, and that's without any of the earthing point/terminal corrosion and general cable degradation inevitable on any 20 year old plus vehicle.
. On my Chimaera I've clearly demonstrated how improving my earths, uprating my cables, fitting a big old Odyssey PC1500 battery and making sure my alternator output is sufficient has made for a far smoother driving and idling TVR, throttle response is better too because the latency between my ECU and injectors has been significantly reduced
The Land Rover part number for the original Magneti Marelli made 100 amp alternator fitted to all serpentine Chimaeras is AMR4247G, you could buy one from a TVR parts specialist but the cost is £153.54 including VAT & delivery and there's no mention of what brand it is, I suspect that means it'll be one of the cheaper makes you could have off EBay for a lot less or they'd be shouting about it being a quality brand.
Interestingly I discovered when Land Rover fitted a heated front screen to Range Rovers & Discoveries in 1997/8 they also uprated the alternator from 100 amps to 120 amps, the body dimensions and mounting points of this higher output alternator are exactly the same as our 100 amp AMR4247G alternator making the 120 amp AMR2938E a direct replacement to AMR4247G.
I wanted a Magneti Marelli or Denso brand alternator, Denso is a quality make you can trust so I started researching how much the Land Rover parts specialists charge for a genuine 120 amp AMR2938E, I got prices ranging from £200 - £150 but eventually found one LR parts specialist selling a genuine Denso brand AMR2938E for £145 including VAT & postage so that's £8 cheaper for the genuine 120a unit than the TVR parts specialists are selling a no-name 100a alternator.
However.... before I pulled the trigger I thought rather than keep Googling 'AMR2938E' I would get Denso's own part number and do a few searches on that, the Denso part number for AMR2938E is DAN016. Searching on DAN016 lead me to an Ebay listing that seemed to be Denso's own Ebay shop, the price looked very good but I called Denso direct to to see if they could better it?
The chap at Denso checked the Ebay listing against my LR part numbers and confirmed it was the right unit, he also said it would be more expensive if I bought through him over the phone because there would be VAT to pay? I didn't question him and simply purchased my brand new genuine Denso AMR2938E / DAN016 120 amp alternator from the Denso Ebay store saving myself the best part of £50 over the best price I could find from a Land Rover parts specialist.
What a great deal
Be careful when searching for a Range Rover V8 alternator, when Land Rover released the Thor engine (still a Rover V8 but with a different inlet manifold) they also changed the alternator, the mounting arrangement is very different so this alternator will not fit our TVRs. However, while the 100 amp AMR4247G ran for quite some time the dimensionally identical AMR2938E (Denso part no: DAN016) only ran for a year or so making it quite rare, everything I'd read about the 120 amp AMR2938E confirmed it's a direct swap for the 100 amp AMR4247G with many Range Rovers owners completing this upgrade.
So a year ago I paid £101.85 delivered for this brand new genuine quality Denso 120amp unit which came marked 'Made In Italy', this is because a few years back Denso bought Magneti Marelli who supplied Land Rover when TVR were taking engines from them so my new alternator is a high quality 100% original equipment component not a pattern copy, just remember to change your 100 amp fuse for a 120 amp one and you're good to go.
Since I bought mine Denso have increased the price of DAN016 to £111.00, but that's still an OEM quality 120a alternator upgrade for a lot less than the TVR parts specialists are charging for a no-name brand 100a unit
https://www.ebay.co.uk/itm/NEW-OE-DENSO-DAN016-ALT...
Here's the dimensions of the 120 amp AMR2938E (Denso part no: DAN016)
And by way of a comparison here's the dimensions of the 100 amp AMR4247G (Denso part no: DAN020)
As we can see they are dimensionally identical, only the amp output differs
Hope all this helps, the links between current sensitive engine management systems (& the associated components it drives) and idle quality/drivability are not to be underestimated! On any fuel injected vehicle, cable gauge, earth quality, battery capacity and sufficient alternator output are all absolutely critical elements of consideration if correct engine behavior is to be achieved
If you ignore the above you may as well run your TVR on a carb, because you'll definitely find it'll run better.
Dave.
thanks - that has really helped my numpty level electrical understanding massively.
the key on the electric PS pump is to have them wired with a switch thingy (not sure what it is called) so it only runs on demand. that's what mine does and, I think, all the T cars have it as well. That reduces the amp load considerably.
the key on the electric PS pump is to have them wired with a switch thingy (not sure what it is called) so it only runs on demand. that's what mine does and, I think, all the T cars have it as well. That reduces the amp load considerably.
jesfirth said:
thanks - that has really helped my numpty level electrical understanding massively.
the key on the electric PS pump is to have them wired with a switch thingy (not sure what it is called) so it only runs on demand. that's what mine does and, I think, all the T cars have it as well. That reduces the amp load considerably.
Hardly numpty driving, boy you can peddle that TVR the key on the electric PS pump is to have them wired with a switch thingy (not sure what it is called) so it only runs on demand. that's what mine does and, I think, all the T cars have it as well. That reduces the amp load considerably.
There must be a pressure switch then, I'd assumed it just ran continuously.
I'd still add up all your current demands, also worth seeing what happens at the alternator, then at the battery, when you both start to turn the steering wheel and in full lock at idle.
Use one of these....
And remember, an alternator won't put out its full rating at idle.
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